The root canal procedure. -

An outline of the steps a dentist follows when they perform root canal treatment (endodontic therapy). | Cleaning and shaping the canals. | Sealing the root canal system. | What is each step like for the patient?

The steps of endodontic therapy.

The following is an outline of the steps a dentist follows when they provide conventional root canal treatment for a tooth. (The basic procedure most frequently performed for teeth.)

Other terms for this procedure are "non-surgical" and "orthograde" endodontic therapy. Both of these names indicate that the procedure is performed through an opening made in the tooth's crown (the portion that lies above the gum line), as opposed to accessing the root directly via some type of surgical procedure.

Step 1 - Placing the rubber dam.

After numbing you up, your dentist will first "isolate" your tooth by way of placing a rubber dam. A dental dam is simply a sheet of "rubber" (actually, latex in most cases) that's pulled over your tooth so it pokes through (see picture below).

As diagrammed on our What is a rubber dam? page, because the portion of the tooth that sticks through the dam now lies in a region where its environment can be controlled, it can be kept contaminate-free during its procedure.

Why is tooth isolation so important?

The barrier created by a dam aids with this goal by preventing saliva (a source of bacteria and debris) from gaining entry into the tooth while its work is being performed.

Note: Placing a dam is part of the "standard of care" that any and every dentist must responsibly provide. If your endodontic procedure doesn't involve using one, you should be asking questions because in the vast majority of cases, it's use is considered absolutely essential. (Ingle)

As alluded above, dental anesthetic doesn't inhibit your sense of pressure. So, when your dentist starts drilling your tooth's access cavity, you'll feel the minor vibrations of their drill. But these mild sensations are really all you should notice.

You shouldn't experience any pain. However, if you find differently, either at this point or during the remainder of your appointment, just indicate to your dentist so they know. (Establishing an agreed upon hand signal with your dentist at the beginning of your appointment makes a good plan.)

Step 3 - Identifying all of the tooth's root canals.

An important aspect of endodontic therapy is that each one is identified and treated. Falling short of this goal will lead to case failure.

A surgical operating microscope may be used.

It's become increasingly common that the floor of your tooth's pulp chamber will be examined using a surgical operating microscope.

These instruments aid the dentist in discovering all of the tooth's root canals by way of helping them to identify the openings of minute canals that might otherwise be overlooked by the naked eye.

Takeaways from this section.

Your dentist searching for the openings to your tooth's root canals should be a non-event. Pain should not be a factor. They'll typically use a pointed hand instrument, or root canal file (see below), to feel around inside your tooth until each one is located.

In cases where a canal's location isn't immediately apparent, your dentist may need to trim away additional portions of your tooth's interior to expose them. If so, at most you should just feel the vibrations of your dentist's dental drill as it's being used.

The use of a microscope increases the likelihood that all of the tooth's canals will be found and therefore treated, which generally translates into increased treatment success.

And that means that with cases where the need to identify very minute canals might be expected (molars, premolars, lower incisors, teeth with calcified pulp chambers and root canals), the use of one could be considered important.

These instruments have a price tag associated with them. So while it's commonplace that an endodontist (root canal specialist) will have one in their office, it's less likely that your general dentist will.

Step 4 - Measuring the length of the tooth.

Your dentist's goal will be one of treating the entire length of each of your tooth's root canals but not beyond. Doing so is not only important for creating treatment success but also helps to minimize complications with post-operative pain.

Meeting this goal means that your dentist must measure the length of each of your tooth's root canals. This measurement is typically calculated to a tolerance of/has an accuracy of 1/2 millimeter (about 1/50th of an inch). (Hargreaves)

Setting the parameters for this measurement.

You might be surprised to learn that there's considerable controversy about just where in a canal its endodontic therapy should terminate.

Some studies suggest that treatment should extend all of the way to the root's apex (tip). Others seem to have concluded that a point 1 to 2 mm shorter gives a better chance of case success. (Hargreaves)

To confuse matters even further, other studies have concluded that the endpoint chosen should be influenced by both the current status of the tooth's pulp tissue (i.e. necrotic, vital, inflamed), and the degree to which the tooth's pathology has affected its surrounding bone tissue. (Hargreaves)

Obviously, choosing the treatment terminus will simply be a judgment call that your dentist will need to make.

How does a dentist make canal length calculations?

There are two methods that a dentist typically uses to measure a canal.

a) By taking an x-ray.

Traditionally, dentists have established/confirmed/documented canal length measurements by way of taking an x-ray after a root canal file has been positioned in it. (Since root canal files are metal, they show up distinctly on an x-ray.)

b) Electronic measurements.

In recent decades, the use of electronic length-measuring devices has become commonplace. These units are referred to as "electronic apex locators." (The word "apex" refers to the tip of the tooth's root.)

Several individual measurements may be needed for a single tooth.

A separate length measurement will need to be made for each of the tooth's individual root canals. (Teeth can have several canals and/or roots.)

What's this step like?

Neither method poses any risk for you feeling anything.

As we discuss on our "Measuring the working length" page linked to above, using the electronic method is quick and simple, and is easily worked into the normal flow of the procedure.

In comparison, the dentist having to stop to take a radiograph tends to interrupt the flow of their work. But the information that an x-ray picture can provide for them can be a great asset to their treatment of your case.

Step 5 - Cleaning and shaping the tooth's root canals.

Its cleaning aspect removes nerve tissue (live and/or dead), as well as bacteria, toxins and other debris harbored inside the tooth. (Here's more detailed information about why this is needed.)

Shaping refers to a process where the contours of the tooth's canals are enlarged and flared, so they have a shape that's more ideal for the procedure's filling and sealing step.

The whole process is a delicate balancing act. One where the dentist seeks to accomplish the goals above, without removing internal tooth structure to an extent, or in a fashion, that might compromise the integrity of the tooth, or the outlook for its completed work.

a) What tools does a dentist use?

For the most part, a tooth is cleaned and shaped (its walls rasped and planed) via the use of root canal files.

What do they look like?

Files look like tapered straight pins but on close inspection you can see, or feel, that their surface is grooved, not smooth. While files come in a couple of different designs, in general terms, they can mostly just be thought of as miniaturized rasps.

Related information - If you'd like more details about files, we delve into this subject much more extensively on our What are root canal files? page.

When this type of set up is used, a tooth's root canal system can usually be cleansed and shaped more rapidly. That can be an important factor in making one-visit root canal treatment possible for a case.

Tooth irrigation is an important part of the cleaning and shaping process.

At minimum, they'll use this as a means of flushing debris and contaminants from within it. Doing so enhances the effectiveness of their cleaning efforts.

But another important function that irrigation provides is to flush away loose debris before it has a chance of being compacted (by the up and down action of the files) into a plug or blockage.

a) What kinds of irrigating solutions are used?

A number of different types of solutions might be chosen:

Conceivably, just sterile water or saline solution could be used to flush out debris.

By far, the most frequently used irrigating solution is sodium hypochlorite (bleach, Clorox). That's because it's effective in killing bacteria and digesting organic debris (two functions that can help to disinfect the tooth's root canal system). It also happens to be quite inexpensive.

Because different solutions have their own set of advantages, your dentist may consider it optimal to use more than one kind of solution during your tooth's treatment.

(Hargreaves - linked above.)

Canal irrigation.

b) How is tooth irrigation performed?

While your dentist may have a specialized unit they use for this purpose, the process they use may be as simple as flushing your tooth out using an "irrigating" syringe.

This is a normal looking, smallish syringe that has a bent/curved, blunt-tipped needle.

The needle is rested inside your tooth and the solution is gently expressed.

(There's nothing sharp about the needle, you are not getting a shot. Gently flushing out the tooth is the goal here, no solution pressure is generated.)

A normal dental suction device is used to catch any excess, or to remove the bulk of the solution from inside the tooth.

c) Why irrigation is such an important part of the root canal procedure.

It's easy to imagine how placing a liquid inside a tooth has the ability to seep into minute nooks and crannies, which are precisely the locations that are impossible for root canal files to access.

And especially in the case where the solution itself has properties that help to disinfect the tooth, this ability can substantially enhance the effectiveness of the dentist's work.

A minimal goal is to have the tooth's root canal system exposed to the irrigant for a period of 30 minutes or longer. (Darcey)

Generally, this step is so beneficial that sometimes the process of "cleaning and shaping" a tooth is instead referred to as "shaping for cleaning," as in the tooth's root canal system is flared and opened up to enhance the volume and access of the irrigation solution used.

For the patient, the cleaning and shaping portion of their tooth's treatment is the most boring part. And as such, the time when they're most likely to fall asleep.

The process itself is just multiple cycles of using files in the tooth ... flushing the tooth out ... and then repeating the process again and again.

During tooth cleaning and shaping.

If your dentist uses a handpiece to manipulate the files, its noise may keep you awake. Or if your tooth is hard to get at, they may have to ask you to open really wide each time they insert the next file into your tooth.

During tooth irrigation.

Your dentist may agitate the solution they place in your tooth with an ultrasonic instrument (its intense vibrations will help to increase the solution's effectiveness). If so, you may hear or feel it's vibrations. Other than that, this whole process should be a non-event.

Bite blocks.

During this step (or anytime during your appointment), if you start to find it hard to stay open, your dentist can put a rubber prop (a "bite block") between your teeth.

[Our slideshow has pictures that illustrate what goes on during this step.]

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Will your tooth's treatment be completed in one or two appointments?

At this point in your tooth's procedure, a potential stopping point has been reached. Its interior has been thoroughly cleansed and properly shaped, and is now ready to be sealed (have its hollow interior filled in).

With some cases, the dentist will go ahead and proceed with this process immediately. (One-visit endodontic therapy.)

With others, they may feel that it's best to wait about a week, or even two or three, before the completion of the tooth's procedure is performed. (Two or more visit treatment.)

The dentist will first select an initial cone of gutta percha for the canal. The size chosen will be the same one as the last (largest) file used to clean and shape the canal's full length (see picture above). This is termed the "master point."

The dentist will evaluate how the master point fits inside its canal both by the way it feels as it's worked into position, and by visualizing it on an x-ray that they'll take. It's important that this first cone extends the full length of the canal, and fits snugly in the region of the root's tip.

If it doesn't, the cone can be removed and adjusted by way of trimming it shorter. Or on occasion, the dentist may find that the next size smaller, or larger, gutta percha cone makes a better choice.

Sealing the tooth's root canal system with gutta percha.

The cone is then removed from the tooth. A sealer (a thin paste) is then applied to its sides, and possibly directly inside the root canal to, and the cone is then reinserted back into position. (Frame "A" in our animation below.)

(The paste enhances the seal that's created by way of filling in any voids that exist between the gutta percha and the walls of the canal.)

Because a master point has a snug fit in the portion of the canal that lies at the root's tip, that cone alone (its single mass of material in conjunction with a thin layer of surrounding sealer) will create the needed seal for that region.

Higher up however, usually the cleaning and shaping process has flared the taper of the upper portion of the canal significantly. And in order to create a solid (free of voids) mass inside the canal to seal it, the dentist will need to place additional cones of gutta percha in this region.

To do so:

The dentist will insert a "spreader" into the canal. (This instrument's working end looks like a root canal file, with the exception that its sides are smooth. It's used as a conically shaped wedge).

Working a spreader inside a root canal. (The master point is visible.)

The spreader is worked laterally (side to side, hence the term "lateral condensation" for this procedure) to compact the gutta percha that's already been placed up against the walls of the canal.

An "accessory point" (a gutta percha point smaller than the master point) is then dipped in sealer and inserted into the space that's been created by the spreader.

This process is then repeated until the entire space within the flared portion of the canal has been filled in (sealed). (Frame "B" in our animation.)

(Tronstad - linked above.)

Lateral condensation technique is just one of the methods your dentist might use. But all processes are the same in the sense that their goal is simply filling in (sealing) the tooth's root canal system with a solid core of material (usually gutta percha and sealer).

What's this step like?

There's not really anything that's all that striking about sealing a tooth, other than it means you're getting close to the end of your appointment.

With some methods, your dentist may heat the gutta percha so it becomes soft and pliable. So, you may smell that.

And you'll feel the pressure of the tools being used in your tooth as the gutta percha being placed is packed and condensed.

Other than that, this step should be yet another non-event in your procedure.

X-ray of a tooth's completed treatment and temporary filling.

Step 7 - Placing a temporary filling.

Once your dentist has finished sealing all of your tooth's individual root canals (many teeth have more than one, see link above), they'll take an x-ray of your tooth so they can evaluate and document their work.

They'll also need to place some type of temporary filling. It will seal off the access cavity created at the beginning of your procedure, therefore protecting the work that's just been completed. (The filling prevents oral bacteria and contaminates from seeping back into the tooth's treated space.)

Take note of the link in Step 7. It details precautions you should take after you tooth's treatment has been completed. (For the most part, don't look for trouble. Just take it easy with your tooth.)

The link in Step 8 is important to understand too. You must have the right type of permanent restoration placed, within the right time frame. Otherwise you put your tooth and its just completed treatment at risk.